Arch Linux on Mac Pro 1.1/2.1

Install Ventoy to a USB stick, download a standard Arch x86_64 ISO and copy it to Ventoy.

Make sure you have a GPU capable of showing Mac EFI as you will need it to boot.

Turn on the computer and hold ALT (on a PC) or Option (on a Mac keyboard).

Select the ISO you wish to boot.

Then choose GRUB2 method.

When in Arch GRUB press e to edit the boot parameters, add noefi as a kernel parameter at the end of the linux line, usually after the timestamp, or the installer will not start. Press F10 to boot. Downloading the initrd and kernel might take some time, be patient.

Install using archinstall as usual, chroot when prompted at the end. Run grub-install --target=i386-efi --efi-directory=/boot --bootloader-id=grub --removable

Edit /etc/default/grub and add noefi to kernel boot params in GRUB_CMDLINE_LINUX_DEFAULT. Run grub-mkconfig -o /boot/grub/grub.cfg This will install a 32-bit EFI version of GRUB and set it to boot. You can now exit chroot and reboot the system. Voila, Arch Linux on Mac 2.1 with 32-bit EFI. Make sure to add a newer GPU that can render your interface.